Lag: Judging off you live in Portugal, it will be massive, you will get kicked out 90% of your games, as Koreans are not like other people alive, Lag is a taboo in Korea.

Guns: they got more than 18 guns -the last time I checked- than NA.AVA
Maps: I think they have 4 or 5 more maps not sure.
Overall: If you weren't considered a pro in NA.AVA, you will feel the urge to shout hacker once or twice per death xD, but there's one weird thing in Korea, their Beginners are way below NA.AVA's beginner's skill level, but their pros are way above NA.AVA's pro's skill level.

you will enjoy KAVA if you have super costy connection and a good sportive spirit.